Double chain stitching method and device for sewing machine

ABSTRACT

In place of the bobbin case containing a lower thread for lock stitching, a double chain stitching element of simple structure is attached to the rotary shuttle of a sewing machine for rotation therewith to provide double chain stitches with an upper thread and a lower thread which is provided in an appropriate position, instead of being provided in the rotary shuttle.

United States Patent [191 Kasuga May 21, 1974 [5 DOUBLE CHAIN STITCHING METHOD 1,143,795 6/1915 Van Horn 112/201 AND D V E FOR SEWING HI 1,264,714 4/1918 Van Horn 112/201 2,132,892 10/1938 Davidson 112/201 [75] Inventor: Noboru Kasuga, o yo, Jap n 3,447,498 6/1969 Eguchi 112/168 ux 3,536,021 10/1970 Kuromegawa 112/168 [73] Assgnee- Ja'wme sew'ng Mach'ne 3,540,390 11/1970 Eguchi 112/228 x Tokyo, Japan 22 Fl ('1: Oct. 17, 1972 1 16 Primary Examiner-Werner H. Schroeder PP 298,076 Attorney, Agent, or Firm--Michael S. Striker [30] Foreign Application Priority Data Oct. 20, 1971 Japan 46-82394 [57] ABSTRACT Cl 112/168, 1 12/201, 112/228 in place of the bobbin case containing a lower thread 112/262 for lock stitching, a double chain stitching element of 1 f D05!) 1305b simple structure is attached to the rotary shuttle of a F 181d of Search 1 201, sewing machine for rotation therewith to provide dou- 112/228, 230 ble chain stitches with an upper thread and a lower thread which is provided in an appropriate position, 1 References Cited instead of being provided in the rotary shuttle.

UNITED STATES PATENTS 752,451 2/1904 Henderson 112/201 5 Claims, 18 Drawing Figures FATENTEDMAY 21 1974 SHEU 1 IF 3 Ff ID;

BRIEF EXPLANATION OF THE INVENTION The present invention relates to double chain stitching method and device for a lock stitching sewing machine. According to the present invention, in a lock stitching sewing machine having a rotary shuttle rotatably mounted in the shuttle holder on the underside of machine bed and adapted to make two rotations to one vertical reciprocation of the needle to produce a lock stitch, a double chain stitching element is attached to the rotary shuttle, in place of a bobbin case containing a lower thread for lock stitching being attached thereto, so that it may rotate with the rotary shuttle to produce double chain stitches with two threads. Besides the double chain stitching element is simple in structure and low in production cost, and applicable to the conventional sewing machines.

Since the conventional devices for producing double chain stitches have been complex in mechanism and difficult in adjustment, double chain stitching sewing machines have been produced to be exclusively used for such a particular purpose. Apart from using such sewing machines in the industrial field, it would be inefficient from the viewpoints of economy and space to use such sewing machines in the general homes. Such a problem has remained to be solved.

The present invention has been provided to eliminate the defects and disadvantages of the conventional sewing machines. The basic object of the invention is to obtain beautiful and well formed double chain stitches by using the double chain stitching element, in place of the bobbin case, attached to the rotary shuttle of a lock stitching sewing machine so that it may rotate with the rotary shuttle, and by using an upper thread just in the same manner as it is used in case of lock stitching and a lower thread which is positioned in an appropriate place, instead of being positioned in the rotary shuttle. Another object of the invention is to smoothly form double chain stitches with utilization ofthe rotary shuttle of lock stitch sewing machine which will well handle the threads at each phase during its two rotations to one vertical reciprocation of the needle. Still another object of the invention' is to obtain double chain stitches only by providing a lower thread supplying device to the conventional sewing machine.

Other features and advantages of the invention will be apparent from the following description in reference to the attached drawing, in which,

FIG. I shows a front elevational view of the double chain stitching element of the invention placed in the rotary shuttle of a lock stitching sewing machine,

FIG. 2 shows a side view of the embodiment of FIG. 1 partly in section,

FIG. 3 shows a plan view of the embodiment in FIG. l partly in section,

FIG. 4 shows a sectional view of the embodiment in FIG. 1 taken along line C C of FIG. 1,

FIG. 5 shows a sectional view of the embodiment in FIG. 1 taken along line D D of FIG. 1,

FIG. 6 shows a perspective view of the double chain stitching element of the invention, and

FIGS. 7(a) 7(i) show a series of analized movements of the rotary shuttle together with the double chain stitching element of the invention.

, edge (12) of inclined annular front wall (13) of rotary DETAIL EXPLANATION OF THE INVENTION In reference to the attached drawing, especially to FIGS. 1 6, numeral 1 denotes a double chain stitching element, which consists of a central cylindrical shaft (4) with a bore (41) and-an enlarged collar portion (4a) by which the element (1) is' removably attached to the rotary shuttle (10), and a substantially flat portion (2) fixed to the front end of cylindrical shaft (4) and provided on the periphery thereof with a cutout to form a hook, inclined surfaces and bent portions which will be described hereinafter more in detail. The rotary shuttle (10) is disclosed in U.S. Pat. No. 3,540,390 and/or U.S. Pat. No. 3,536,022 owned by the same applicant.

1n the flat portion (2), a hook end (31) of hook (3) is defined by means of an oblique cutout (21) and is positioned above the surface of flat portion (2) as particularly shown in FIG. 3. In the direction opposite to the direction in which the hook (3) rotates, the flat portion (2) is provided with a V shaped groove (5), and the outer curved edge (32) of hook (3) is continued to one end (52) of the groove (5) and also the upper face (33) of hook 3) is inclined toward the groove (5) and continuous therewith. On the outside of V shaped groove (5) opposite to the flat portion (2), there is provided an upwardly enlarged tongue (6) which is at the middle part thereof outwardly bent to form a ridge (7) in the same level as the upper surface (22) of flat portion 2) while the linear edge (71) of the groove is located below the level of upper surface (22) of flat portion (2) and is continued to the end 52) of V shaped groove (5) through a curved edge (71a).

As particularly shown in FIG. 5, when the double chain stitching element (1) is positioned in the rotary shuttle (10), the outer edge (62) of tongue (6) is located adjacent to but spaced from the thread tightening shuttle, and also located substantially on the line connecting the edge'(12) and the bottom (51) ofV shaped groove (5). As particularly shown in FIG. 4, with provision of oblique cutout (21), the flat portion (2) is provided with a thread guide (8) opposite to the hook (3). The thread guide (8) has an inclined face (81) just like inclined face (33) of hook (3) and an end (82) located in a level lower than that of thread tightening edge (12) of rotary shuttle (10) and spaced therefrom when the element (1) is mounted in the rotary shuttle.

In the peripheral realm between the end (53) of V shaped groove (5) and the thread guide (8), the flat portion 2) is provided with an inclined face (9) which is just like the inclined wall (13) of rotary shuttle (10). At the junction of the inclined face (9) and the thread guide (8), there is formed a shoulder (83) to hold a thread. The inclined face (9) is also spaced from the thread tightening edge (12) of rotary shuttle (10) when the element (1) is mounted in the rotary shuttle.

As particularly shown in FIGS. 3 and 4, the cylindri-- cal mounting shaft (4) of the double chain stitching element (1) is partly formed with an-axial groove (42) communicating with the bore (41). A detaining spring (43) is fixedly mounted on the collar portion (4a) by means of a fastening screw. The forward end (44) 0f the spring (43) is extended into the bore (41) through the groove (42) while the rearward end (45) of the spring (43) is extended a little in parallel with the cylindrical shaft (4).

When the double chain stitching element (1) is mounted in the rotary shuttle on its'mounting shaft (11), the rearward end (45) of detaining spring (43) engages a driving cutout (15) or rotary shuttle (l0), and the forward end (44) of detaining spring (43) engages the annular groove (14) of the mounting shaft (11) or rotary shuttle (10). Thus the element (1) is fixedly mounted in the rotary shuttle (10) in such a manner that the hookend (31) of the element (1) is positioned in a place a little backward in the rotating direction from the line connecting the hookend (18) of the rotary shuttle (l0) and its rotation axis (0). It is apparent that the double chain stitching element (1) will be rotated with the rotary shuttle (10) which is then rotatably mounted in the shuttle holder (16) partly shown in FIG. 7; however it is not illustrated in the series of front elevational views to clearly show the relative movements of the threads and the rotary shuttle l0) containingthe double chain stitching element (1). In FIG. 7, a lower thread guide (17) is arranged on the front and left hand side from the vertical line passing through the center (0) of the rotary shuttle (l0) and at a position below the rotary shuttle 10).

To explain the operation of the present invention in reference to a series of rotation processes of the rotary shuttle (10) as illustrated in FIGS. 7(a) 7(i), FIG. 7(a) shows the rotary shuttle (10) starting to rotate in the direction indicated by the arrow, and also shows a lower thread ($2), the thread source of which (not shown) is provided in an appropriate place outside of the rotary shuttle (10), passing through the thread guide (17) and led to the underside of a work piece (not shown) on the needle plate slantwise of the front side of rotary shuttle l0) and double chain stitching element (1) to tighten the work with the upper thread (81) and is placed under the pressure of presser foot (not shown). The lower thread (S2),contacts the upper parts of rotary shuttle (I0) and the element l) and the needle is moving upward from the lowest dead point in the rotary shuttle (10) to form a thread loop, and reference mark S2 denotes a loop of the lower thread (82) formed during a preceding cycle of operation.

As the rotary shuttle (10) starts to rotate in the direction indicated by the arrow. the double chain stitching element (1) will rotate with the rotary shuttle in the same direction, and the hook (3) of the element (1) catches the lower thread (S2) as shown in FIG. 7(b) and FIG. 7(bb), the latter being a vertical section of the former, to guide a part of the lower thread to the rear side of the hook (3) while the hook 18) of the rotary shuttle (10) catches a loop of upper thread (S1) when the needle (20) is in the process of upward movement.

(S2) is guided to the central part of the flat portion (2) on the rear side thereof while the upper thread loop (S1) is partly guided by the rotary shuttle (10) over the inclined tongue (6]) to the flat portion (2) on the front side thereof and is partly guided to the center of the rotary shuttle (10) on the rear side thereof. Thus the upper thread loop formed from thread (S1) is most enlarged around the rotary shuttle (10), and the lower thread (S2) comes to be inserted into the upper thread loop. 7

As the rotary shuttle (10) further rotates and comes to the stage shown in FIG. 7(a), the upper thread (81) is pulled up and the upper thread loop is reduced by means of the conventional thread take up lever (not shown), and accordingly the lower part of the lower thread (S2) is brought up by the upper thread loop to make an are around the rotation axis (0) of the rotary shuttle (l0) and of the element (1), on the rear side of the flat portion (2). At this stage, the rotary shuttle (10) has made one complete rotation from the starting stage shown in FIG. 7(a).

In the stage of FIG. 7(/), as the rotary shuttle further rotates, the upper thread loop is brought up to the upper side of the needle plate while the lower thread (S2) passes through the small loop of upper thread (S1) from the work (not shown) to round up around the rotation axis (0) of the rotary shuttle (10) on the rear side of the element l) and again passes through the upper thread loop to be led to the thread guide (17). In this process, a part of the lower thread S2) is engaged by the thread guide (8) of the element (1) and brought to the front side of the flat portion (2) since the thread guide (8) is, as aforementioned in reference to FIG. 4, downwardly inclined and the tip (82) is located in thelevel lower than the thread tightening edge (12) of rotary shuttle (l0). I

In the stage of FIG. 7(g) and FIG. 7(gg), the latter being a vertical section of the former, the feed dog operates to feed the work (not shown) for a pitch while another part of the lower thread (S2) is engaged by the inclined face (33) of hook (3) and brought to the front side of the flat portion (2) and is further guided over the flat surface (22) towards the rotation center (0) of the rotary shuttle (l0) and the element (1).

In the stage of FIG. 7(h), as the rotary shuttle (l0) and the element(l further rotate, the lower thread (S2) is partly held by the thread holding shoulder (83) 0f the element (1) and is partly held by the inclined tongue (6) of the element (I).'The tongue (6), however, holds a little part of the lower thread (S2) be cause the lower thread is tightened on the side of the tongue (6) bymeans of the thread tightening edge 12) of the rotary shuttle (10). As the result, the loop formed from lower thread (S2) takes on an enlarged, substantially triangular configuration with the needle hole (19) of the needle plate being at a peak of the triangle'so that the descending needle (20) with the upper thread (Sl) may enter the triangular loop of lower thread S2).

In the stage of FIG. 7(i), the needle (20) reaches the lower dead point and at the same time the loop of lower thread (S2) held by the double chain stitching element (1) is narrowed on both sides thereof over the flat portion (2) of the element (1). As the rotary shuttle (10) further rotates, the lower thread (S2) is released by the element (1) at a place where the thread holding shoulder (83) and the inclined tongue (6) are shifted with the rotation together with the rotary shuttle (10), while the lower thread (S2) passing through the thread guide (17) is tensioned by means of a proper device (not shown). I I

In such a manner, a double chain stitch is produced, and accordingly with repetition of the same cycles as shown in FIGS. 7(a) 7(1'), successive double chain stitches are made, in which FIGS. 7(a) and 7(b) show that the hook (18) of the rotary shuttle catches the upper thread loop formed in the loop made from the lower thread (S2).

According to the present invention, it has been made possible to obtain double chain stitches, which would otherwise have to be made by means of a special industrial sewing machine, with a general domestic sewing machine having a rotary shuttle, by placing a special double chain stitching element, in place of the bobbin case, in the rotary shuttle.

l claim:

1. A method of producing double chain stitches with a sewing machine having a vertically reciprocating needle and a rotary shuttle which rotates twice during each reciprocation of the needle, comprising the steps of mounting a double chain stitching element in said shuttle for rotation therewith; catching an upper needle thread with said shuttle during rotation thereof, and forming of said upper needle thread a first thread loop about said shuttle; catching a lower thread with said chain stitching element during rotation of the same, and forming of said lower thread a second thread loop about said element; inserting said second thread loop into said first thread loop; inserting the needle together with said upper needle thread into said first thread loop; and tightening said lower thread and thereby said second thread loop about said first thread loop, subsequent to insertion of said needle and upper needle thread into said first thread loop.

2. A method as defined in claim 1, said sewing machine having a needle plate formed with a hole, and said element and shuttle each having a front face and a hook; and comprising the steps of leading said lower thread from below said shuttle across said front faces to said hole of said needle plate; inserting said second thread loop into said first thread loop around said shuttle while said first thread loop is engaged as said shuttle rotates; and inserting said needle together with said upper needle thread into said second thread loop to form in the latter an additional loop; catching said first said element.

thread loop with said hook of said shuttle; and catching said lower thread and tightening said second thread loop with said hook of said element.

3. In a sewing machine, a combination comprising a vertically reciprocable needle engaging an upper needle thread; a shuttle holder downwardly of said needle; a rotary shuttle mounted in said shuttle holder and being rotatable twice during each reciprocation of said needle, said shuttle having a first portion for catching said needle thread and forming therefrom a first thread loop about said shuttle; and double chain stitching element means rotatably mounted in said shuttle and having one portion for catching a lower thread which extends towards said needle and forming therefrom a second thread loop about said element means, and another portion for inserting said second thread loop into said first thread loop preliminary to entry of said needle and upper needle thread into said first thread loop, and for tightening said second thread loop about said first thread loop subsequent to such entry.

4. A combination as defined in claim 3, said shuttle having a hollow body provided with an opening which is bounded by an annular thread-tightening edge surrounding an axis of rotation of said shuttle; and said element means comprising a mounting component within said hollow body, and a flat component provided on said mounting component and located outside said body adjacent said annular edge.

5. A combination as defined in claim 4, wherein said portion of said element means comprise a hook positioned in a plane spaced from said flat component so as to catch said lower thread and guide the same to one side of said flat component, a thread guide spaced from said hook in direction of rotation of said element for engaging said lower thread and guiding the same from said one side to an opposite side of said flat componentto form said second loop and a tongue which engages said second thread loop when the same is guided to said opposite side for maintaining said second loop open until entry of said needle and upper needle thread, and for releasing said second loop during further rotation of 

1. A method of producing double chain stitches with a sewing machine having a vertically reciprocating needle and a rotary shuttle which rotates twice during each reciprocation of the needle, comprising the steps of mounting a double chain stitching element in saiD shuttle for rotation therewith; catching an upper needle thread with said shuttle during rotation thereof, and forming of said upper needle thread a first thread loop about said shuttle; catching a lower thread with said chain stitching element during rotation of the same, and forming of said lower thread a second thread loop about said element; inserting said second thread loop into said first thread loop; inserting the needle together with said upper needle thread into said first thread loop; and tightening said lower thread and thereby said second thread loop about said first thread loop, subsequent to insertion of said needle and upper needle thread into said first thread loop.
 2. A method as defined in claim 1, said sewing machine having a needle plate formed with a hole, and said element and shuttle each having a front face and a hook; and comprising the steps of leading said lower thread from below said shuttle across said front faces to said hole of said needle plate; inserting said second thread loop into said first thread loop around said shuttle while said first thread loop is engaged as said shuttle rotates; and inserting said needle together with said upper needle thread into said second thread loop to form in the latter an additional loop; catching said first thread loop with said hook of said shuttle; and catching said lower thread and tightening said second thread loop with said hook of said element.
 3. In a sewing machine, a combination comprising a vertically reciprocable needle engaging an upper needle thread; a shuttle holder downwardly of said needle; a rotary shuttle mounted in said shuttle holder and being rotatable twice during each reciprocation of said needle, said shuttle having a first portion for catching said needle thread and forming therefrom a first thread loop about said shuttle; and double chain stitching element means rotatably mounted in said shuttle and having one portion for catching a lower thread which extends towards said needle and forming therefrom a second thread loop about said element means, and another portion for inserting said second thread loop into said first thread loop preliminary to entry of said needle and upper needle thread into said first thread loop, and for tightening said second thread loop about said first thread loop subsequent to such entry.
 4. A combination as defined in claim 3, said shuttle having a hollow body provided with an opening which is bounded by an annular thread-tightening edge surrounding an axis of rotation of said shuttle; and said element means comprising a mounting component within said hollow body, and a flat component provided on said mounting component and located outside said body adjacent said annular edge.
 5. A combination as defined in claim 4, wherein said portion of said element means comprise a hook positioned in a plane spaced from said flat component so as to catch said lower thread and guide the same to one side of said flat component, a thread guide spaced from said hook in direction of rotation of said element for engaging said lower thread and guiding the same from said one side to an opposite side of said flat component to form said second loop and a tongue which engages said second thread loop when the same is guided to said opposite side for maintaining said second loop open until entry of said needle and upper needle thread, and for releasing said second loop during further rotation of said element. 